This application is based on Japanese patent application No.2001-292978 filed in Japan on Sep. 26, 2001, the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal composition and a liquid crystal light modulating apparatus using the liquid crystal composition.
2. Description of Related Art
The liquid crystal light modulating apparatus basically comprises a pair of substrates and a liquid crystal layer disposed between the substrates. When a drive voltage is applied to the liquid crystal layer, the arrangement of liquid crystal molecules is controlled so that light incident on the liquid crystal light modulating apparatus is modulated to perform a desired image display.
A wide variety of liquid crystal display methods have been proposed.
In recent years, research has been conducted on liquid crystal light modulating apparatuses using a chiral nematic liquid crystal composition containing a chiral material so that the composition is caused to exhibit a cholesteric liquid crystal phase at room temperature due to the chiral material.
It is known that this type of liquid crystal light modulating apparatus is useful, for example, as an apparatus which can be driven with a low consumption of electric power utilizing a selective reflection capability of the chiral nematic liquid crystal composition.
In the reflection type liquid crystal light modulating apparatus, image display can be performed by applying a high or low pulse voltage to switch the liquid crystal composition to a planar state (colored state) or to a focal conic state (transparent state).
Even after stopping the application of such pulse voltage, the liquid crystal composition can be held in the planar state, the focal conic state or a mixed state, in other words, can exhibit the so-called bi-stable property and can achieve a memory effect, whereby the image display can be kept after stopping the application of voltage.
Such liquid crystal light modulating apparatus using the chiral nematic liquid crystal composition is required to achieve a high performance in image display such as enhanced color purity and high reflectance, to show a sharp contrast and involve a low drive voltage.
An object of the invention is to provide a chiral nematic liquid crystal composition which is useful for providing a liquid crystal light modulating apparatus which can achieve a high performance in image display such as enhanced color purity and high reflectance, can show a sharp contrast and involves a low drive voltage.
Another object of the invention is to provide a liquid crystal light modulating apparatus which can achieve a high performance in the image display such as enhanced color purity and high reflectance, can show a sharp contrast and involves a low drive voltage.
The inventors conducted extensive research to achieve the foregoing objects and found the following.
In a liquid crystal light modulating apparatus comprising a pair of substrates at least one of which is transparent and a chiral nematic liquid crystal composition disposed between the substrates and comprising a nematic liquid crystal composition and a chiral agent, a high performance such as enhanced color purity and high reflectance can be achieved in image display, a sharp contrast is shown and a low drive voltage is involved, when the chiral nematic liquid crystal composition comprises 55 wt % to 90 wt % of a nematic liquid crystal composition that comprises, as main components thereof, a liquid crystal ester compound and a fluorine-containing liquid crystal pyrimidine compound, and 10 wt % to 45 wt % of at least one kind of chiral agent, the chiral nematic liquid crystal composition being able to exhibit a cholesteric phase (at about 25xc2x0 C.).
The present invention was completed based on the above-described findings and provides a chiral nematic liquid crystal composition and a liquid crystal light modulating apparatus as described below.
(1) Chiral Nematic Liquid Crystal Composition
The present invention provides a chiral nematic liquid crystal composition that exhibits a cholesteric phase, and that comprises 55 wt % to 90 wt % of a nematic liquid crystal composition that comprises, as main components thereof, a liquid crystal ester compound and a liquid crystal pyrimidine compound, wherein the liquid crystal ester compound does not include a tolan skeleton therein and the liquid crystal pyrimidine compound includes a fluorine atom therein; and 10 wt % to 45 wt % of at least one chiral agent.
The amount (wt %) of the nematic liquid crystal composition and the amount (wt %) of the chiral agent are values per 100 wt % of the total weight of the nematic liquid crystal composition and the chiral agent.
(2) Liquid Crystal Light Modulating Apparatus
The present invention also provides a liquid crystal light modulating apparatus comprising a pair of substrates at least one of which is transparent, and the aforementioned chiral nematic liquid crystal composition disposed between the substrates.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.